UA professor developing prosthesis that works like a real leg

Molei Wu, a mechanical engineering graduate student at the University of Alabama, demonstrates how an above the knee prosthesis works at the South Engineering Research Center on Monday. Xiangrong Shen, an assistant professor of mechanical engineering at UA, is hoping to use the same technology to create a below the knee prosthesis.

Michelle Lepianka Carter | Tuscaloosa News

By Kim EatonStaff Writer

Published: Tuesday, November 20, 2012 at 1:31 p.m.

Last Modified: Tuesday, November 20, 2012 at 1:31 p.m.

TUSCALOOSA | Xiangrong Shen has a goal — to improve the quality of life for amputees. To do this, he is developing a prosthesis that functions and feels like human muscle.

“When you build something to replace a human limb, you want the device to be as similar as possible (to the limb),” said the University of Alabama associate professor of mechanical engineering. “You want the same mechanism that is in the human body.”

Current leg prosthetics are energetically passive, which means they can only dissipate energy, or store and reuse energy in walking. As a result, the amputee's other joints have to work harder, which causes the amputee to use more energy, leading to an unnatural walk, Shen said.

“That's the problem we want to solve,” he added.

For the past six years, Shen has been researching and developing a flexible, robotic actuator that functions like a biological muscle. Initially, he focused on above-knee amputees, but with the help of a recently received $564,000 grant from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, Shen can now work on developing a below-knee prosthesis that will be able to power the ankle joint in use.

There are two primary components in the new prosthesis: a special class of liquid fuel called monopropellant and a sleeve muscle actuator, which is an artificial muscle that replaces the motor used in current prosthesis. The monopropellant generates a large amount of hot gas and decomposes upon contact with certain catalysts, Shen said, resulting in the storage of enough energy to operate daily a light-weight prosthesis. The sleeve actuator is also lighter, more powerful and similar to a biological muscle, he added.

While the main functions of the device will be similar to an above-knee prosthesis, the specific design will be different and a challenge to create. When working with above-knee amputees, the actuator has various biological components to attach to, but for a below-knee prosthesis, the device needs to be as small and short in length as possible so it can fit people with amputations close to the ankle, Shen said. The computer controller will also need to be small enough to fit on the prosthesis so the device will be a self-contained system, he added.

The four-year grant will include preliminary testing on the various components, followed by testing on human patients when the device is completely finished.

“It's going to be lighter, and closer to human muscle,” Shen said. “And if we can use that technology to drive the prosthesis, then the user can gain more mobility. That's what this is all about.”

<p>TUSCALOOSA | Xiangrong Shen has a goal — to improve the quality of life for amputees. To do this, he is developing a prosthesis that functions and feels like human muscle.</p><p>“When you build something to replace a human limb, you want the device to be as similar as possible (to the limb),” said the University of Alabama associate professor of mechanical engineering. “You want the same mechanism that is in the human body.”</p><p>Current leg prosthetics are energetically passive, which means they can only dissipate energy, or store and reuse energy in walking. As a result, the amputee's other joints have to work harder, which causes the amputee to use more energy, leading to an unnatural walk, Shen said. </p><p>“That's the problem we want to solve,” he added.</p><p>For the past six years, Shen has been researching and developing a flexible, robotic actuator that functions like a biological muscle. Initially, he focused on above-knee amputees, but with the help of a recently received $564,000 grant from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, Shen can now work on developing a below-knee prosthesis that will be able to power the ankle joint in use.</p><p>There are two primary components in the new prosthesis: a special class of liquid fuel called monopropellant and a sleeve muscle actuator, which is an artificial muscle that replaces the motor used in current prosthesis. The monopropellant generates a large amount of hot gas and decomposes upon contact with certain catalysts, Shen said, resulting in the storage of enough energy to operate daily a light-weight prosthesis. The sleeve actuator is also lighter, more powerful and similar to a biological muscle, he added.</p><p>While the main functions of the device will be similar to an above-knee prosthesis, the specific design will be different and a challenge to create. When working with above-knee amputees, the actuator has various biological components to attach to, but for a below-knee prosthesis, the device needs to be as small and short in length as possible so it can fit people with amputations close to the ankle, Shen said. The computer controller will also need to be small enough to fit on the prosthesis so the device will be a self-contained system, he added.</p><p>The four-year grant will include preliminary testing on the various components, followed by testing on human patients when the device is completely finished. </p><p>“It's going to be lighter, and closer to human muscle,” Shen said. “And if we can use that technology to drive the prosthesis, then the user can gain more mobility. That's what this is all about.”</p><p><i>Reach Kim Eaton at kim.eaton@tuscaloosanews.com or 205-722-0209</i></p>